Li, C., Cen, S., Chen, X., F, L. C., & Xiang-Rong, F. (2009). Quadrilateral membrane elements with analytical element stiffness matrices formulated by the new quadrilateral area coordinate method (QACM-II). International Journal for Numerical Methods in Engineering, 77(8), pp. 1172-1200. doi:10.1002/nme.2459

Li, Chenfeng, Song Cen, Xiao-Ming Chen, Li C. F, and Fu Xiang-Rong. "Quadrilateral Membrane Elements With Analytical Element Stiffness Matrices Formulated By the New Quadrilateral Area Coordinate Method (QACM-II)." International Journal for Numerical Methods in Engineering 77, no. 8 (2009): 1172-1200.

Li, Chenfeng, et al. "Quadrilateral Membrane Elements With Analytical Element Stiffness Matrices Formulated By the New Quadrilateral Area Coordinate Method (QACM-II)." International Journal for Numerical Methods in Engineering 77.8 (2009): 1172-1200.